This invention relates to gear reducers and more particularly to a freeing mechanism for a motorized gear reducer.
Motorized gear reducers incorporating motors are widely used now. JP-B-64-5176, for example, discloses a reducer for reducing the rotation caused by a hydraulic motor via a planetary differential gear reducer in order to take out the output. According to this JP-B-64-5176, the output thus taken out is used to drive a crawler vehicle, for example.
When the motor in such a conventional motorized gear reducer as mentioned above malfunctions for some reason or other, the output portion of the gear reducer becomes unable to be moved because the motor and the gear reducer are integrally coupled together. Particularly when the motorized gear reducer like this is used in a vehicle traveling apparatus, any attempt to have the vehicle repaired by coupling the vehicle to a towing vehicle and sending it to a predetermined repair shop will result in necessitating an extremely large power for towing the vehicle as the motor is unseparable from the gear reducer and the problem is that the vehicle in need of repair becomes practically untransportable.
In view of the foregoing problems, an object of the present invention is to provide a motorized gear reducer so adapted that when it is needed to operate the motorized gear reducer freely for some reason or other, the whole of the motorized gear reducer can easily be operated by releasing the gear reducer from being coupled to the motor and applying small force to the output side of the gear reducer.
To achieve the above-noted object, the present invention provides a freeing mechanism for a motorized gear reducer comprising: a driving motor; an input rotary shaft coupled to the driving motor; first and second external gears meshing with each other; and a movable shaft member selectively coupling the first external gear to the input rotary shaft.
The movable shaft member is axially movable between first and second positions relative to the input rotary shaft and the first external gear so that the movable shaft in the first position is engaged with both the input shaft and the first external gear to establish an integral rotation condition, and the movable shaft in the second position is engaged with one of the input rotary shaft and the first external gear but disengaged from the other of the input rotary shaft and the first external gear to establish a free rotation condition.
In a preferred embodiment, a motorized gear reducer is constructed such that a first external gear is mounted on an input rotary shaft coupled to a driving motor and a second external gear is capable of engaging with the first external gear. The front end portion of the first external gear side of the input rotary shaft is unable to make a relative rotation with respect to the input rotary shaft but made movable in the axial direction of the input rotary shaft. The front end portion thereof movably axially engages with the first external gear. The front end portion thereof and the first external gear are allowed to select one of the conditions including making an integral rotation and freely making relative rotations in accordance with the axial movement of the front end portion thereof.
In this arrangement, the front end portion of the input rotary shaft coupled to the driving motor is made movable in the axial direction of the input rotary shaft, and the front end portion thereof and the first external gear are allowed to select one of the conditions including making the integral rotation and freely making relative rotations in accordance with the axial movement of the front end portion thereof. Consequently, when it is needed to free the motorized gear reducer for some reason or other, the coupling of the driving motor to the reducer is released by setting free the front end portion of the input rotary shaft from the first external gear, so that the reducer can be operated by applying small force to the output side of the gear reducer.
Although the invention can be implement in gear reducers in general, it is also applicable to a planetary differential gear reducer having a reduction gear in the preceding stage as disclosed in JP-B-64-5176. In this case, the second external gear is preferably coupled to the crank pin of the planetary differential gear reducer.
According to the specific embodiment of the invention, the motorized gear reducer is such that the front end portion of an input rotary shaft on the first external gear side includes a cylindrical member which is integrally mounted to the front end portion of the body of the input rotary shaft and has a spline groove at the front end of the first external gear side, and a shaft member which is axially movably joined to the cylindrical member by way of a spline joint; the shaft member axially has a shaft-side spline having a predetermined length at the front end on the first external gear side; the base side of the first external gear is cylindrical; and in the hollow portion of the first external gear, there are formed a cylinder-side spline engaging with the shaft-side spline formed for the shaft member by way of spline engagement, and a large-diameter hole portion 41b not engaging with the shaft-side spline by way of spline engagement.
The front end portion of the input rotary shaft is thus formed with the cylindrical member having the spline groove and the shaft member joined to the spline groove so as to hold the cylindrical member in such a state that the coupling of the cylindrical member to the shaft member may be maintained. With the formation of the shaft-side spline having the predetermined length in the front end portion of the cylindrical member, the shaft-side spline is allowed to select one of the conditions including making the cylindrical portion on the base side of the first external gear engage with the cylinder-side spline and disengage therefrom, whereby the input rotary shaft and the first input rotary shaft are allowed to select one of conditions wherein both are engaging with each other and set free from engaging with each other.
In this case, the front end portion on the input rotary shaft side preferably has a spring member for engaging the shaft-side spline with the cylinder-side spline by way of spline engagement by normally urging the shaft member toward the first external gear side. Thus, the shaft member is normally kept engaging with the first external gear.
In order that the shaft member and the first external gear are allowed to select one of the engagement and free conditions, the reducer includes a cover member located outside the first input rotary shaft, a pin member engaging with the axial front end of the shaft member of the input rotary shaft and a recessed member engaging with the outer-side front end of the pin member. Further, the shaft-side spline and the cylinder-side spline are preferably allowed to select one of the spline engagement and free conditions depending on the direction of mounting the recessed member.
The shaft-side spline is joined to the cylinder-side spline when the recessed member in the outwardly recessed condition is mounted, whereas the shaft member is forced inside when the recessed member in the inwardly recessed condition is mounted, in accordance with the direction of mounting the recessed member. The shaft-side spline and the cylinder-side spline are reduced to the free condition, whereby their joined and freed conditions can be attained quite simply. In order to simplify the movement of the shaft member in particular, the recessed member is joined to the cover member with a bolt, whereby detachably providing the recessed member results in simplifying the movement of the shaft member without using special tools.
In order to allow the relative rotation of the shaft member with respect to the pin member for pressing the shaft member in this case, a small-diameter ball is preferably provided in the front end portion of the shaft member so as to allow the input rotary shaft together with shaft member to rotate.
It is also preferable that internal teeth of a spline formed on the first external gear and external teeth of a spline formed on the front end portion of the input rotary shaft on the first external gear side are used to disengageably couple the input rotary shaft to the first external gear, and tooth thickness of at least one of the internal and external teeth is gradually decreased at and near axial ends of the internal and external teeth where they are initially engaged when said front end portion is axially moved. This preferable arrangement makes it possible to carry out the engagement between the external and internal teeth of the spline smoothly.
Similarly, it is also preferable that internal teeth of a spline formed on the first external gear and external teeth of a spline formed on the front end portion of the input rotary shaft on the first external gear side are used to disengageably couple the input rotary shaft to the first external gear, and tooth height of at least one of the internal and external teeth is gradually decreased at and near axial ends of the internal and external teeth where they are initially engaged when said front end portion is axially moved. This preferable arrangement makes it possible to carry out the engagement between the external and internal teeth of the spline smoothly.
The present disclosure relates to the subject matter contained in Japanese patent applications Nos. Hei. 11-84201 (filed on Mar. 26, 1999), and Hei. 11-247015 (filed on Sept. 1, 1999), which are expressly incorporated herein by reference in their entireties.